LEl'IDOUANOIDEI 



39 



evidence of the full development of the ganoid order. In the 

 lowest or " triassic " division this order is still represented by 

 heterocercal and notochordal species belonging to some of the 

 genera of the Permian period, as, e. g., Ccelacanthus, Ambhjp- 

 tcrus, and Pakconiscus. The genus Placodus, a supposed 

 pycnodont fish of the muschelkalk, has been shown to be a 

 conchivorous Saurian* 



In the oolitic division the heterocercal Ganoids are almost 

 completely superseded by homocercal genera, which now, for 

 the first time, appear on the stage of life ; but the ossification 

 of the endo-skeleton is still incomplete. In the cretaceous 

 series the Teleostian, or well-ossified, bony fishes, are nume- 

 rous ; and here also first are seen fishes with the flexible 

 " cycloid" or " ctenoid" scales, and of genera which continue 

 to be represented by living species. 



Of 33 genera of fishes in the lias, 4 only were represented 

 in older strata, while the rest extend into the upper oolitic 

 beds. Of these, 19 genera are Ganoids with rhomboid scales, 

 and two (Leptol&pis and Gyrosteus) have rounded scales. 



Family VII. — Caturid.e. 

 Homocercal rhombo-ganoids, with a short dorsal fin, and some 

 of the teeth much larger than the rest and laniariforrn. 



Genus Catukus. — In this genus the jaws are armed with 



' P 

 Fig. 53. 

 Caturus furcatus (Oolite, Solenhofen). 



close-set, large, conical teeth ; the scales are delicate : the fins 

 * Owen, in Phil. Trans. 1858, p. 169. 



